A combination of electrospray ionization (ESI) and ion mobility mass spectrometry (IMMS) is used to successfully determine the characteristic ratio (Cn) of homopolymers and triblock copolymers. Two different copolymer systems are analyzed: a poly(ethylene glycol)/poly(propylene glycol) (PEG/PPG) and a poly(methyl acrylate)/poly(butyl acrylate) (PMA/PBA) based system. The monomer composition within the copolymers is chosen to be constant while changing the block sequence along the main chain, in order to ensure a reliable determination of the influence of the topology on the physical properties. It can be demonstrated that the block structure has a significant influence on Cn and therefore on the physical properties of the block copolymers. For both systems, the inner block dominates the overall physical properties.